//! Virtual display orchestration (plan §6) — the project's differentiator.
//!
//! A [`VirtualDisplay`] creates a *client-sized* output on demand, rendered natively and
//! headless (no scaling), to be captured and streamed, then torn down on disconnect. There is
//! no cross-compositor Wayland protocol for this, so each compositor has its own backend behind
//! this trait:
//!
//! * **KWin** — privileged `zkde_screencast_unstable_v1::stream_virtual_output` ([`kwin`]).
//! * **wlroots/Sway** — `swaymsg create_output` + `output mode --custom` ([`wlroots`]).
//! * **Mutter/GNOME** — D-Bus `RemoteDesktop` + `ScreenCast.RecordVirtual` ([`mutter`]).
//!
//! [`VirtualDisplay::create`] returns a [`VirtualOutput`]: the PipeWire node to capture plus an
//! owned keepalive whose `Drop` releases the output (RAII — no explicit `destroy`). Capture
//! consumes the node via [`crate::capture::capture_virtual_output`].

use anyhow::Result;
pub use punktfunk_core::Mode;
use std::os::fd::OwnedFd;

/// A created virtual output: a PipeWire source to capture, plus an owned keepalive whose drop
/// tears the output down (releases the compositor-side resource).
///
/// Allowed dead on non-Linux: the backends that construct it are all `cfg(target_os = "linux")`.
#[allow(dead_code)]
pub struct VirtualOutput {
    /// PipeWire node id of the output's screencast stream.
    pub node_id: u32,
    /// Portal/remote PipeWire fd when the node lives on a sandboxed remote (e.g. Mutter's
    /// RemoteDesktop+ScreenCast). `None` means the node is on the user's default PipeWire daemon
    /// (KWin `zkde_screencast`), captured by connecting to that daemon directly.
    pub remote_fd: Option<OwnedFd>,
    /// `(width, height, refresh_hz)` to prefer in the PipeWire format negotiation. KWin and
    /// gamescope outputs are created at the exact size, so this just confirms it; **Mutter sizes
    /// its virtual monitor FROM the negotiation**, so here it's what makes the client's mode real.
    pub preferred_mode: Option<(u32, u32, u32)>,
    /// Keeps the output — and whatever connection/thread backs it — alive; dropped on teardown.
    pub keepalive: Box<dyn Send>,
}

/// Pluggable virtual-output creation, per compositor.
pub trait VirtualDisplay: Send {
    /// Human-readable backend name (e.g. `"kwin"`, `"wlroots"`, `"mutter"`).
    fn name(&self) -> &'static str;
    /// Create a virtual output of the given mode. Teardown is RAII: drop the returned
    /// [`VirtualOutput`]'s `keepalive`.
    fn create(&mut self, mode: Mode) -> Result<VirtualOutput>;
}

/// Compositors punktfunk knows how to drive (plan §6).
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum Compositor {
    /// KWin / Plasma 6 — `zkde_screencast` virtual output.
    Kwin,
    /// wlroots (Sway/Hyprland) — headless `create_output`.
    Wlroots,
    /// Mutter / GNOME — headless backend + Mutter DBus `RecordVirtual`.
    Mutter,
    /// gamescope — spawned headless at the client's size/refresh; capture its PipeWire node.
    Gamescope,
}

impl Compositor {
    /// Stable lowercase id used on the wire / management API (matches
    /// [`punktfunk_core::CompositorPref::as_str`]).
    pub fn id(self) -> &'static str {
        match self {
            Compositor::Kwin => "kwin",
            Compositor::Wlroots => "wlroots",
            Compositor::Mutter => "mutter",
            Compositor::Gamescope => "gamescope",
        }
    }

    /// Human label for UIs.
    pub fn label(self) -> &'static str {
        match self {
            Compositor::Kwin => "KWin / KDE Plasma",
            Compositor::Wlroots => "wlroots (Sway / Hyprland)",
            Compositor::Mutter => "Mutter / GNOME",
            Compositor::Gamescope => "gamescope",
        }
    }

    /// The protocol [`punktfunk_core::CompositorPref`] naming this backend.
    pub fn as_pref(self) -> punktfunk_core::CompositorPref {
        use punktfunk_core::CompositorPref as P;
        match self {
            Compositor::Kwin => P::Kwin,
            Compositor::Wlroots => P::Wlroots,
            Compositor::Mutter => P::Mutter,
            Compositor::Gamescope => P::Gamescope,
        }
    }

    /// The concrete backend a [`punktfunk_core::CompositorPref`] names, or `None` for `Auto`.
    pub fn from_pref(p: punktfunk_core::CompositorPref) -> Option<Compositor> {
        use punktfunk_core::CompositorPref as P;
        Some(match p {
            P::Auto => return None,
            P::Kwin => Compositor::Kwin,
            P::Wlroots => Compositor::Wlroots,
            P::Mutter => Compositor::Mutter,
            P::Gamescope => Compositor::Gamescope,
        })
    }

    /// Every backend, in a stable display order (for enumeration / UIs).
    pub fn all() -> [Compositor; 4] {
        [
            Compositor::Kwin,
            Compositor::Gamescope,
            Compositor::Mutter,
            Compositor::Wlroots,
        ]
    }
}

/// The compositor backends usable on this host *right now*: gamescope wherever its binary is
/// installed (it spawns a nested session — independent of the running desktop), plus the live
/// session's own compositor (KWin / Mutter / wlroots) when the host runs inside it. Cheap,
/// side-effect-free probes — safe to call per management request. A concrete client preference
/// is validated against this set before it's honored (see the m3 handshake's resolution).
pub fn available() -> Vec<Compositor> {
    #[cfg(target_os = "linux")]
    {
        let mut v = Vec::new();
        if kwin::is_available() {
            v.push(Compositor::Kwin);
        }
        if gamescope::is_available() {
            v.push(Compositor::Gamescope);
        }
        if mutter::is_available() {
            v.push(Compositor::Mutter);
        }
        if wlroots::is_available() {
            v.push(Compositor::Wlroots);
        }
        v
    }
    #[cfg(not(target_os = "linux"))]
    {
        Vec::new()
    }
}

/// Detect the compositor to drive: `PUNKTFUNK_COMPOSITOR` override, else `XDG_CURRENT_DESKTOP`.
pub fn detect() -> Result<Compositor> {
    if let Ok(v) = std::env::var("PUNKTFUNK_COMPOSITOR") {
        return match v.trim().to_ascii_lowercase().as_str() {
            "kwin" | "kde" | "plasma" => Ok(Compositor::Kwin),
            "wlroots" | "sway" | "hyprland" | "wlr" => Ok(Compositor::Wlroots),
            "mutter" | "gnome" => Ok(Compositor::Mutter),
            "gamescope" => Ok(Compositor::Gamescope),
            other => {
                anyhow::bail!(
                    "unknown PUNKTFUNK_COMPOSITOR '{other}' (kwin|wlroots|mutter|gamescope)"
                )
            }
        };
    }
    let desktop = std::env::var("XDG_CURRENT_DESKTOP")
        .unwrap_or_default()
        .to_ascii_uppercase();
    if desktop.contains("KDE") {
        Ok(Compositor::Kwin)
    } else if desktop.contains("GNOME") {
        Ok(Compositor::Mutter)
    } else if desktop.contains("SWAY")
        || desktop.contains("WLROOTS")
        || desktop.contains("HYPRLAND")
    {
        Ok(Compositor::Wlroots)
    } else {
        anyhow::bail!(
            "could not detect compositor from XDG_CURRENT_DESKTOP='{desktop}'; set PUNKTFUNK_COMPOSITOR"
        )
    }
}

/// Open the virtual-display driver for `compositor`.
pub fn open(compositor: Compositor) -> Result<Box<dyn VirtualDisplay>> {
    #[cfg(target_os = "linux")]
    {
        match compositor {
            Compositor::Kwin => Ok(Box::new(kwin::KwinDisplay::new()?)),
            Compositor::Gamescope => Ok(Box::new(gamescope::GamescopeDisplay::new()?)),
            Compositor::Mutter => Ok(Box::new(mutter::MutterDisplay::new()?)),
            Compositor::Wlroots => Ok(Box::new(wlroots::WlrootsDisplay::new()?)),
        }
    }
    #[cfg(not(target_os = "linux"))]
    {
        let _ = compositor;
        anyhow::bail!("virtual displays require Linux (Wayland compositor)")
    }
}

/// Readiness probe for `compositor`: is it up and able to create a virtual output *right
/// now*? A session-bringup script polls this (via `punktfunk-host probe-compositor`) to gate
/// on actual readiness instead of racing the compositor with a blind sleep.
///
/// KWin gets a real check (the privileged `zkde_screencast` global must be advertised). The
/// others are spawn/D-Bus/portal-based and have no equivalent pre-flight global, so a probe
/// just confirms the backend opens — `Ok(())` means "go ahead and try `create`".
pub fn probe(compositor: Compositor) -> Result<()> {
    #[cfg(target_os = "linux")]
    {
        match compositor {
            Compositor::Kwin => kwin::probe(),
            // gamescope spawns its own nested session per `create`; Mutter is D-Bus on demand;
            // wlroots creates the output on demand — nothing to pre-check beyond "Linux".
            Compositor::Gamescope | Compositor::Mutter | Compositor::Wlroots => Ok(()),
        }
    }
    #[cfg(not(target_os = "linux"))]
    {
        let _ = compositor;
        anyhow::bail!("virtual displays require Linux (Wayland compositor)")
    }
}

/// Path of the file where the gamescope backend relays the nested session's `LIBEI_SOCKET`
/// (gamescope's EIS server) for the input injector.
#[cfg(target_os = "linux")]
pub fn gamescope_ei_socket_file() -> &'static str {
    gamescope::EI_SOCKET_FILE
}

#[cfg(target_os = "linux")]
mod gamescope;
#[cfg(target_os = "linux")]
mod kwin;
#[cfg(target_os = "linux")]
mod mutter;
#[cfg(target_os = "linux")]
mod wlroots;